CODEWITHSUNDEEP
javascriptarraysfunctionobjectrecursion
coolps811
coolps811

Reputation: 323

How to recursively map/restructure an object?

I would like an array of objects with all object keys from a nested object. I wrote a recursive function to do this however at the point that the function is recalled it is not going through the object as expected but rather sending back an index infinitely.

let array = [];

const findKeys = (ob) => {
  let id = 0;
  let keys = Object.keys(ob);
  for (let i = 0; i < keys.length; i++) {

    let object = {
      id: id,
      label: keys[i],
    };

    array.push(object);
    id ++;
    findKeys(ob[keys[i]]);
  }
  return array;
};

let newArray = findKeys(data);
console.log(newArray);

example data structure:

const data = {a: {
  b: {
    c: {
      foo: 'bar'
    }
  }
}}

Upvotes: 0

Views: 1069

Answers (4)

Scott Sauyet
Scott Sauyet

Reputation: 50797

Here is a simple technique, using a fairly generic, depth-first, key-collecting traversal, followed by a mapping to add the indices:

const flattenKeys = (o) =>
  Object (o) === o
    ? Object .entries (o) .flatMap (([k, v]) => [k, ...flattenKeys (v)])
    : []

const getKeys = (o) =>
  flattenKeys (o) .map ((label, id) => ({label, id}))

const data = {a: {b: {c: {foo: 'bar'}}}}

console .log (getKeys (data))
.as-console-wrapper {max-height: 100% !important; top: 0}

If you wanted a breadth-first traversal it wouldn't be much harder.

This separation of key collection and index generation makes the code much simpler to my mind.

Upvotes: 0

Redu
Redu

Reputation: 26161

Perhaps you may do like

var data = {a: {
  b: {
    c: {
      foo: 'bar',
      arr: [1,2,3,4]
    }
  }
}};

function getAllKeys(obj){
  var keys = (typeof obj === "object") && (obj !== null) && Object.keys(obj);
  return !!keys ? keys.reduce((r,k) => r.concat(getAllKeys(obj[k])),keys)
                : [];
};

var res = getAllKeys(data);

console.log(JSON.stringify(res));

Upvotes: 0

Mister Jojo
Mister Jojo

Reputation: 22320

some thing like that

see also Check that value is object literal?

const data = { a: { b: { c: { foo: 'bar' } } }}

const isObject = el => (Object.prototype.toString.call(el) === '[object Object]')

const findKeys = obj => 
  {
  let arr   = []
    , id    = 0
    ;
  getKeys(obj)
  return arr

  function getKeys(o)
    {
    Object.keys(o).forEach(key =>
      { 
      arr.push({ id:id++, label:key })
      if (isObject(o[key]))
        getKeys(o[key])
      })  
    }
  }
  

console.log( findKeys(data) )
.as-console-wrapper {max-height: 100%!important;top:0 }

Upvotes: 0

epascarello
epascarello

Reputation: 207511

You need to check to see if you have an object before you do the next recursive call. You also are resetting id so you are going to have the ids repeated (maybe you want that?) and you are using a global for the array so it can not be used more than once.

You are going to want something like:

function getKeys(obj) {

  const array = [];
  let id = 0;

  function loop(obj) {
    Object.entries(obj).forEach(entry => {
      array.push({
        id: ++id,
        label: entry[0],
      });      
      if(entry[1] != null && entry[1].constructor.name === "Object") {
        loop(entry[1]);
      }
    });
  }

  loop(obj);

  return array;
}

const obj1 = { a: 1, b: 'bar' };
console.log(getKeys(obj1));

const obj2 = { a: 1, b: { c: 'bar' } };
console.log(getKeys(obj2));

Upvotes: 2

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